Mixed carboxylate derivatives of basic alkaline earth metal sulfonates



United States Patent 3 446,736 MIXED CARBOXYLA'IE DERIVATIVES 0F BASICALKALINE EARTH METAL SULFONATES Richard S. Herd and Ferdinand P. Otto,Woodbury, N.J., assignors to Mobil Oil Corporation, a corporation of NewYork No Drawing. Filed Feb. 8, 1968, Ser. No. 703,868 Int. Cl. ClOm 3/34US. Cl. 25233.2 16 Claims ABSTRACT OF THE DISCLOSURE Overbased,carbonated alkaline earth metal sulfonates, having a metal content atleast 200% higher than that of a corresponding normal metal sulfonatesalt, are reacted with formic acid and a second carboxylic acidcontaining from 2 to about carbon atoms to provide improved oilsolubledetergents for lubricants and as an additive for fuels. The process forpreparing these oil soluble salts requires at least two steps in whichthe formic acid is reacted with the said sulfonate first followed by thereaction with the second carboxylic acid. The ratio of chemicalequivalents of acids ranges from about 40:1 to 1:4 of formic acid to thesecond carboxylic acid.

BACKGROUND OF THE INVENTION Field of the invention This inventionrelates to oil soluble, overbased alkaline earth metal sulfonatederivatives and to methods for preparing the same, and in particular, itrelates to mixed carboxylate derivatives of the sulfonates.

Description of the prior art US. Patent No. 2,763,615 deals with thereaction product of a low molecular weight monocarboxylic acid With abarium salt of a sulfonic acid. However, this reference only discloseslow-metal containing salts. U.S. Patent No. 3,027,325 disclosespreparing a mixture of calcium sulfonate, calcium hydroxide, Water andalcohol in an oil and reacting with carbon dioxide. There is nodisclosure in this reference of reaction 'with an acid.

SUMMARY OF THE INVENTION It has now been discovered that alkaline earthmetal carbonate-sulfonate salts may be reacted with formic acid and asecond carboxylic acid having from 2 to 5 carbon atoms whereby the metalcarbonate portion of the salt is converted to the formate-carboxylate toproduce liquid, oil-soluble products which possess improvedcharacteristics in lubricating oil. The ratio of formic acid to the C toC acid may range from about 40:1 to 1:4, and preferably from 1021 to1:3.

DESCRIPTION OF SPECIFIC EMBODIMENTS It has been found that the reactionof metal carbonatemetal sulfonate salts, as they are also referred toherein, with acetic acid or higher acids result in the formation ofgel-like, oil-insoluble masses. As such, they would be unsuitable foruse as a fluid lubricant. On the other hand, the reaction of thesecarbonate-sulfonate salts with formic acid alone, in the presence of adiluent, preferably an oil diluent, produce excellent, liquidoil-soluble detergents and corrosion inhibiting additives. The basicityof the salts is high enough to prevent the corrosion caused by acidsderived from oxidation of the oil or combustion of sulfur containingfuels. Occasionally, however, the water stability of such formic acidderivatives, while satisfactory, is not always optimum. It is,therefore, surprising to discover that by converting the carbonateportion of the sulfonate salts to the formate initially and thenconverting the remaining portion of the carbonate to a highercarboxylate, until substantially all of the carbonate has beenconverted, the resulting salts remain liquid and oil soluble. Thebasicity is retained at the level required to help prevent corrosion ofmetal surfaces in the engine and the Water stability is considerablyimproved. If desired, some of the metal carbonate may still be permittedto remain in the reaction product. Complete conversion of the carbonateis not essential.

For the sake of simplicity, the products of the present invention andthe overbased metal sulfonates from which they are obtained willhereinafter be referred to using terminology such .as metalsulfonate-metal carbonate or metal carbonate-overbased metal sulfonatefor the intermediate product and metal sulfonate-metal carboxylate ormetal carboxylate-overbased metal sulfonate for the final product, orsimilar expressions. The precise structure of the metalcarboxylate-containing products of the instant invention is not known.Without limiting the invenion to any particular theory, it is believedthat the several components form a product of the dispersion orcolloidal suspension type wherein the mixed metal carboxylates are heldin dispersion or suspension by the metal sulfonate.

A variety of overbased, metal sulfonate-metal carbonate salts, which aresuitable for use in the mixed carboxylic acid reaction of the presentinvention, are shown in the art. Typical of these and, indeed,preferred, are the metal carbonate-overbased metal sulfonates describedin US Patent Nos. 2,616,911 and 2,956,018.

As disclosed in US. in US. Patent No. 2,956,018, these metalcarbonate-overbased, metal sulfonates may be prepared by admixing aninorganic compound of a basic metal, such as an alkaline earth metaloxide or hydroxide with an aliphatic monohydric alcohol containing 1 to5 carbons such as methanol. A metal carbonate reagent is then formed bypassing carbon dioxide through this admixture of the basic metalcompound and the aliphatic alcohol. This metal carbonate reagent isreacted with a sulfonic acid or sulfonic acid salt to form the metalcarbonate-overbased metal sulfonate, which is reacted with thecarboxylic acids according to the present invention.

In view of the fact that calcium sulfonate-calcium carbonates are ofspecial interest, the following is a further more specific descriptionof one of the preferred methods of preparing a calcium sulfonate-calciumcarbonate which may be used in the preparation of the high metal contentoverbased, metal sulfonates of the present invention.

The formation of the calcium sulfonate-calcium carbonate involves thepreparation of a calcium carbonate reagent in methanol and the reactionof this reagent with a sulfonic acid or sulfonate salt. The resultingcalcium sulfonate-calcium carbonate is then reacted with formic acid anda second acid to form our metal mixed-carboxylate products.

More particularly, the aforementioned calcium carbonate reagent may beprepared by carbonating wit carbon dioxide a suitable calcium inorganiccompound such as calcium oxide or hydroxide in methanol. For example,the reagent may be prepared by first forming a suspension of the calciumcompound, e.g., calcium hydroxide in absolute methanol, adjusting thetemperature of this suspension to below approximately 30 C., preferablyso that amount of carbon dioxide absorbed is suCh as to provide a molration of carbon dioxide to calcium therein of from about 0.6 to about2.0.

The resulting calcium carbonate reagent is then reacted with a suitablesulfonic acid or metal salt thereof as follows. The chilled (IO-30 C.)reagent is intermixed with a solution of the sulfonic acid or salt inmineral oil and the mixture is heated to a temperature above the boilingpoint of methanol to facilitate reaction and effect removal of themethanol by distillation. After the distillation step, the reactionmixture is filtered, preferably while hot, to provide the highmetal-content calcium sulfonate-calcium carbonate.

A sufiicient amount of mineral oil is preferably employed as solvent inthe reaction between the calcium carbonate reagent and the sulfonic acidor salt in order to maintain the reaction mixture fluid and thusfacilitate the final filtration and handling of the product which wouldotherwise be quite viscous. Other hydrocarbon solvents besides mineraloil or in addition to mineral oil, such as light naphtha, xylene,toluene, benzene, etc., may be employed.

The amount of calcium carbonate reagent employed in the reaction withthe sulfonic acid or salt should, of course, be sufiicient to providethe excess metal which is incorporated into the salt product. Thus, atleast about 3 equivalents and up to about 31 equivalents or more ofcalcium should be provided in the reagent where the sulfonic acid per se(i.e., unneutralized) is used and at least about 2 equivalents and up toabout 30 or more of calcium, where a neutral sulfonic acid salt isutilized in the process, the said equivalents being on the basis of theacid-hydrogen equivalents of the sulfonic acid or the neutral sulfonicacid salt.

Other methods of preparing carbonated, basic alkaline earth metal saltsmay be used, such as simply reacting an alkaline earth metal oxide orhydroxide with a sulfonic acid or normal sulfonate salts in the presenceof a lower aliphatic alcohol, such as methanol, and passing carbondioxide therethrough.

The sulfonic acids from which the calcium sulfonatecalcium carbonateintermediates are prepared, or, indeed, any of the metal sulfonate-metalcarbonates, include oilsoluble petroleum and synthetic alkaryl sulfonicacids, particularly those having molecular weights of from about 300 toabout 1500. These acids may be produced by sulfonation of petroleumstocks or synthetic alkyl aromatic compounds, such as alkyl substitutedbenZenes and naphthalenes, wherein the alkyl groups attached to the aromatic ring contain at least about 12 carbon atoms and preferably from atleast about 14 to about 24 or more, carbon atoms. Suitable syntheticsulfonic acids are, for example, octadecyl-benzene sulfonic acid. Of thevarious acids, the wax benzene and wax-naphthalene sulfonic acids andmixed alkyl aromatic sulfonic acids are preferred. The petroleumsulfonic acids, also known as sour oils, are those obtained in thetreatment of petroleum oils, particularly refined or semi-refined oil,with concentrated or fuming sulfuric acid, and which remain in the oilafter settling out of sludge. These sulfonic acids may be represented bythe general formula:

R S OaI-I where R is one or more alkyl, alkaryl or aralkyl groups andthe aromatic nucleus is a single or condensed ring or partiallyhydrogenated ring. Other suitable sulfonic acids, such as aliphaticsulfonic acids, derived from polyolefins having a molecular weight offrom 300 to 1500, parafiin wax, and the like, may be used in thisinvention.

Although the preparation of the calcium carbonate-overbased, calciumsulfonate intermediate has been referred to in some detail, it should benoted that the present invention is applicable to any overbased, metalsulfonate containing a metal carbonate as the overbase material whereinthe metal is an alkaline earth metal. It will also be appreciated thatany of this type of metal carbonateoverbased, metal sulfonate productsmay be employed in the formic acid-C to C acid reaction regardless oftheir particular method of preparation.

Overbased metal sulfonate-metal carbonate compositions wherein the metalused is an alkaline earth metal,

4 preferably calcium, barium, or strontium, are reacted initially withformic acid followed by the reaction with the higher carboxylic acid.The total equivalents of acid added to the reaction mixture ispreferably sufficient to at least substantially convert all of the basiccarbonate to the mixed carboxylate. There is thus approximately onetotal equivalent of the acids per equivalent of carbonate employed inproducing the products of this invention. The reaction with the acids isconducted at slightly elevated temperatures to high temperatures.Temperatures in the range of from about 50 to about 225 C., preferablyfrom about 100 to 200 C., are suitable. If a diluent for the reactionmixture is used, it is preferably a refined mineral oil and mayconstitute from 20% to of the reaction mixture.

The reaction product may be recovered in any suitable manner, such as byfiltration, wherein the desired reaction product is recovered as thefiltrate. Satisfactory filtration results are obtained by adding a smallamount of a sulfonic acid to either the formic acid or the C to C acidor both used in the reaction step. Any sulfonic acid may be mixed withthe carboxylic acid. For example, sulfonic acids, such as thosehereinabove mentioned as suitable for use in the preparation of themetal sulfonate-metal carbonate products may be employed. The rate offiltration may be further improved if the reactions between thecarboxylic acids and the metal sulfonate-metal carbonate are conductedat temperatures from about to about 200 C.

The criticality of reacting the metal carbonate-overbased metalsulfonate with formic acid first is demonstrated by the fact thatcorresponding metal acetate-overbased metal sulfonates are gel-like,insoluble masses unsuitable for use in producing fiuid lubricating oils.Reaction of the sulfonate-carbonate with formic acid as the first step,followed by reaction with the C to C acid prevents gelation of thereaction product. If desired, the acid reaction may be performed in aseries of 2, 3, 4, or more steps providing always that the first stepinvolves reacting formic acid alone Formic acid must not be premixedwith the higher acid in the initial step. Hence, in the first step,formic acid is reacted with a portion of the carbonate component. Thesecond step consists of reacting with acetic acid or higher molecularweight acid. If desired, the first two steps may convert only a portionof the carbonate. A third step may consist of reacting more formic acidor even a third acid with the remainder of the carbonate or this stepmay in turn be followed by a fourth reaction with a higher acid,providing the ratio of acid equivalents is met. Mixtures of C to C acidsmay, of course, be used.

The C to C acids consist of acetic acid, propionic acid, butyric acidand valeric acid or the anhydrides thereof, and branched isomers aswell. As much as 4 to 1 of the higher acids to formic acid may beemployed, however, higher mole ratios result in gelation.

The metal mixed carboxylate-overbased metal sulfonates of this inventionpossess additive properties superior to those of the corresponding metalcarbonate-overbased metal sulfonates. Thus, our metal carboxylateproducts inhibit the deposit-forming tendencies, increase the hightemperature stability and improve the anti-wear properties oflubricating oils to a significantly greater extent than do thecorresponding metal carbonate products.

The metal carboxylate-overbased metal sulfonate products of thisinvention are further distinguishable from metal sulfonate productsheretofore known, by virtue of their remaining liquid even withexceedingly high metal contents. Thus, the metal contents of our metalcarboxylate overbased products are from 200' percent up to about 2000percent or more, higher than that of the corresponding normal salts,i.e. salts having metal contents equivalent to the acid hydrogencontents having the respective sulfonic acids from which they arederived.

The production of metal carboxylate-overbased metal sulfonatescontaining such high metal contents is due to the specific procedureutilized in our synthesis. According to this aspect of the invention,the metal carboxylate-metal sulfonate product is produced by goingthrough the carbonate group of the metal carbonate-overbased metalsulfonate, that is, by first forming the metal carbonate-overbased metalsulfonate and then converting this product to a metal mixedcarboxylate-overbased product by reaction with formic acid followed bythe C to C acid. The importance of this specific process procedurebecomes apparent when it is realized that metal sulfonate-metalcarboxylate products, such as calcium sulfonate-calcium carboxylateproducts, possessing metal contents from 200 percent up to 2000 percentor more higher than that of the corresponding normal salt, as far as weare aware, cannot be prepared directly from a sulfonic acid or calciumsulfonate and a carboxylate. According to the best of our knowledge,only by carrying out the instant formic acid reaction initially is itpossible to produce such extremely high metal content calciumsulfonate-calcium carboxylate oil-soluble products, since there isbelieved to be no other effective way of introducing such amounts ofcalcium carboxylate other than by going through the carbonate group.

These metal sulfonate-metal carboxylate products are of particularinterest as additives for marine diesel cylinder lubricants wherein theyinhibit the deposit-forming tend encies especially the port cloggingtendencies which result from the use of high sulfur content fuels inthese engines, and act to improve the anti-wear characteristics of thelubricating oils These metal carboxylate overbased products may also beused, for example, in lubricating oils for railroad diesel engines, gasengines, as well as in as various other types of lubricants for internalcombustion engines. It will be appreciated, however, that the productsof the present invention may be advantageously used in a variety ofmineral oil lubricating compositions. The products may also be used ingasoline and fuel oil for de tergency or other utility, i.e. reductionof corrosion.

The particular amounts of the metal carboxylate-overbased sulfonateproduct used in the final fiuid compositions will depend on factors suchas the nature of the base stock, its intended use, the presence of otheringredients, etc. In general, the overbased sulfonate product may bepresent in an amount from about 0.05 to 50 percent by Weight of thebase, or higher, if desired. In the case of marine diesel oils higherproportions in the range of from about to 40 percent, preferably topercent are used. On the other hand, in automotive engine oils, 0.5 to20 percent, preferably 1 to 10 percent of the additive may be used.

It will of course, be appreciated that the mineral oil compositionscontaining the instant overbased sulfonate product may, of course, alsocontain efiective quantities of various other typical lubricating oiladditives, such as pour point depressants, V.I. improvers, extremepressure agents, anti-oxidants, etc.

The following examples are presented to illustrate more clearly thenature of the present invention. It should be understood, however, thatthe invention is not limited to these specific embodiments.

Example 1 shows the procedure for the preparation of a calciumsulfonate-calcium carbonate product which is of the type reacted withformic acid and the C to C acid in the succeeding working examples.

EXAMPLE 1 A slurry of 148 grams (4.0 true equivalents) of calciumhydroxide in two liters of absolute methanol was charged into a 5-literflask, chilled below 15 C. in an ice-bath and carbonated to a carbondioxidezcalcium ratio of 1.9 (162 grams, 7.4 equivalents of C0 Theslurry thickened considerably during the carbonation. The rate ofcarbonation was followed by noting the increase in weight of thereaction flask.

A mixture of 600 grams (0.67 true equivalents) of a mixed wax-benzene(2-l2)-alkyl aromatic sulfonic acid 6 having a total N.N. of 68 and atrue N.N. of 63 and 600 grams of diluent oil (a parafiinic oil having aviscosity of 100 SUS at 100 F.) was heated in a beaker to 60 C. andadded to the carbonated reagent.

The methanol was removed through a Dean-Stark takeoff by heating thereaction mixture to C. over 6% hours and then maintaining thetemperature at 90100 C. for 1 /2 hours with vigorous nitrogen blowing.

Sixty grams of Hyflo (a diatomaceous earth filter aid) was added and themixture filtered through an electrically heated Buchner funnel precoatedwith Hyfio giving a bright fluid product having the following analysis:

Total calcium, percent 5.3. Perchlorie acid base No. (mg.

KOH/g. sample) 120 r4.3% calcium. Excess calcium, percent 430.

EXAMPLE 2 One-hundred grams (0.214 equivalents of CO of a calciumsulfonate-calcium carbonate product (4.7% CO 5.1% Ca., 121 TBN, preparedaccording to Example 1 were charged into a 250 ml., 4-neck round-bottomflask equipped with a mechanically driven glass paddle type stirrer anda thermometer. The charge was heated to 90 C. and 5.0 grams (0.098equivalents) of 90.5% formic acid were added slowly above surfacedropwise. After the formic acid addition, the reaction mixture in theflask Was heated to 120 C. and 5.1 grams (0.089 equivalents) of 97.4%acetic anhydride was added dropwise. During the acetic anhydrideaddition, 50 grams of a solvent refined mineral oil diluent was alsoadded. The reaction product was then heated at 150 C. with a stream ofnitrogen for one hour, and 7.5 grams of diatomaceous filter aid wasadded to the mixture. The mixture was filtered through diatomaceousfilter aid on a heated Buchner funnel. The resulting product was aliquid.

Analysis of product:

Calcium percent 3.1 Carbon dioxide do 0.91 Formic acid 1 do 1.8 Aceticacid do 2.9 'Perchloric acid base No. (mg. KOH/g. sample) 74 1 Asformate and acetate of calcium.

EXAMPLE 3 To 500 grams (1.07 equivalents of CO of a calciumsulfonate-calcium carbonate product similar to that used in Example 2was added a mixture of 25 grams (0.49 equivalents) of 90.5 formic acidand 29 grams (0.485 equivalents) of acetic acid at 90 C. The mixed acidswere added dropwise. After only approximately one-half of the acidmixture had been added, the product gelled.

This example illustrates that a gel is obtained when the formic acid ispre-mixed with a C to C carboxylic acid.

EXAMPLE 4 To grams (0.215 equivalents of CO of the calciumsulfonate-calcium carbonate product of Example 2 was added 2.5 grams(0.049 equivalents) of 90.5 formic acid dropwise at 90 C. Afterward, thereaction mixture was heated to C. and 5.1 grams (0.097 equivalents) of97.4% of acetic anhydride was added slowly above the surface dropwise.The reaction mixture was cooled to 90 C. and another 2.5-gram portion(0.049 equivalents) of formic acid was added in the same manner asbefore. After the acid additions were completed, the mixture was heatedto C. in a stream of nitrogen for one hour. The mixture was cooled to120 C. and 5 grams of diatomaceous earth filter aid was added. Themixture was filtered through diatomaceous earth filter aid on a heatedBuchner funnel. The resulting product was a liquid.

7 Analysis of product:

Calcium percent 4.9 Carbon dioxide do 18 Formic acid 1 do 2.8 Aceticacid 1 do 4.3 Perchloric acid base No. (mg. KOH/ g. sample) 114 1 Asformate and acetate of calcium.

EXAMPLE 5 To 150 grams (0.30 equivalents of CO of a calciumsulfonate-calciurn carbonate product similar to that used in Example 2was added 3.65 grams (0.072 equivalents) of 90.5% of formic acid at 85C. dropwise. The reaction mixture was heated to 120 C. and 3.75 grams(0.072 equivalents) of 97.4% of acetic anhydride was added slowly abovethe surface dropwise. The reaction mixture was cooled to 90 C. again andthe two steps were repeated using the same conditions and amounts ofacids as used in the first two steps, so that a total of about 0.288equivalents of the acids were obtained in the four acid additions. Themixture was heated to 150 C. in a nitrogen stream for one hour. Themixture was then cooled to 120 C., and 7.5 grams of diatomaceous earthfilter aid was added. The product was filtered through diatomaceousearth filter aid on a heated Buchner funnel. The resulting product was aliquid.

Analysis of Product:

' To two samples of 100 grams of the calcium sulfonatecalcium carbonateused in Example 2 were added acetic anhydride and acetic acid,respectively, in equivalent amounts. When approximately /2 the acid hadbeen added, in each case the reaction mixture gelled.

EXAMPLE 7 To 500 grams (2.18 equivalents of CO of an overbased calciumsulfonate-calcium carbonate product containing 11.2% Ca, 9.6% CO and a303 TBN in a 1 liter, 4-n eck round bottom flask equipped with amechanically driven glass paddle stirrer, thermometer, a subsurfacedropping funnel, and a water receiver adapted for nitrogen sparging anda condenser was added 61.2 grams (1.2 equivalents) of 90% formic acid at200 C. A stream of nitrogen was used. The formic acid was added in twoportions over an hour period each. A thirty minute hold time wasmaintained during the additions. The reaction mixture was maintained at200 C. for /2 hour and 61.6 grams (1.2 equivalents) of 99.5% aceticanhydride was added in two portions using the same conditions as withthe formic acid addition. The mixture was heated at 200 C. for one hour,cooled to 150 C., and 25 grams of diatomaceous earth filter aid wasadded. The mixture was filtered through diatomaceous earth filter aid ona heated Buchner funnel. The product was a liquid.

Analysis of Product:

Using the same conditions, equipment and amount of sulfonate complex asin Example 7, the amount of fomric acid was 31 grams (0.6 equivalents)and the amount of acetic anhydride was 93.5 grams (1.8 equivalents). Theproduct Was a liquid.

Analysis of Product:

Calcium percent 10.6

Carbon dioxide do 3.8

Sulfur do 0.6

Base No. (HClO mg. KOH/g. 286

KV at 210 F cs 241.6

EXAMPLE 9 in three equal portions. The product was a liquid.

Analysis of Product:

Calcium percent 10.1 Carbon dioxide do 3.6 Sulfur do .76 Base No. (HClOmg. KOH/g. 282 KV at 210 F cs 159.0

EXAMPLE 10 To 2500 grams (10.9 equivalents of CO of the sulfonateproduct of Example 7 were added 513 grams (about 9 equivalents) offormic acid at 200 C. dropwise. The addition was made in 3 portions. Themixture was maintained at 200 C. and 57 grams (about 1 equivalent of99.5% acetic anhydride) was added in 1 portion. At the end of the acidadditions, the reaction product was treated as in Example 7. The productwas a liquid.

Analysis of Product:

Calcium percent 10.3

Carbon dioxide do 2.5

Sulfur do 0.69

Base No. (HCIOQ mg. KOH/g 2.84

EXAMPLE 11 Following the same procedure as in Example 7, 19 grams (0.372equivalent) of 90% formic acid was added to the sulfonate product at 200C., then 106.3 grams (2.04 equivalents) of acetic anhydride was to beadded in three separate portions. The first addition took one hour. Thereaction mixture became a solid gel during the second addition.

Evaluation of products The fluid products of this invention wereevaluated in the panel coker test and in the water stability test.

Panel coker test.This test is used to determine the tendency oflubricants to form solid decomposition products when in contact withhigh temperature surfaces; this tendency indicating the hightemperature, oxidation stability of the oil formulation.

A sample of the lubricant is splashed onto a Weighed polished aluminumtest panel. The test panel is heated and placed in a coking apparatus insuch a position that the polished surface thereof is exposed to contactwith oil thrown against it by means of a splasher immersed in the oil.The test panel is heated to a temperature of 600 F. and maintained atthis temperature while the splasher is on and off operated for a periodof 24 hours. The splasher operates 15 seconds out of every minute. Afterthe test, the panel is removed, cooled, washed, dried, and reweighed.The difference in weight before and after the test is the amount ofsolid combustion deposits. Comparison with base stocks containing otherformulations indicates the relative oxidation stability at hightemperatures of the formulation components presently being tested.

To a mixture of parafiinic solvent refined mineral oils of SAE 30 wasadded 13.6% by weight of the calcium sulfonate-calcium carbonatereactant of Example 7 (Composition A). To a second sample of the samebase stocks were added 14.1% of the carboxylate product of Example 7(Composition B). Each sample of oil was formulated to provide a 40 TBNoil. The following results were obtained:

Composition: Weight deposit, mg. A 540 B 196 Water stability test-Inthis test, an oil formulation is evaluated for ability of a formulatedoil ot separate from water as completely as possible so that no waterremains in the oil phase. Often, the presence of oil additives, such asdetergents have emulsifying tendencies in which case many suchformulated oils perform poorly in this test.

The oil formulation to be tested is mixed vigorously with by volume ofdistilled water for three minutes and then allowed to stand for 24hours. The results are rated by visual means. A rating of very good isone in which the oil and water separate togive 95% and 5% of each phase.If some water remains in the oil phase but the separation is still 95%'and 5% oil-in-water respectively, the rating is good.

To the same base stocks are used in the panel coker test, containing aminor amount of a commercial calcium additive, was added 29.1% of aformated product of the calcium sulfonate-calcium carbonate salt used inExample 7. Such products are described and claimed in copendingapplication Ser. No. 282,548 (Composition C). To a second sample of abase blend was added 28.1% of the carboxylate product of Example 7(Composition D). To a third base blend was added 28.0% of the product ofExample 8, (Composition E). The following results were obtained:

The mixed formate-C -to-C carboxylate products of this inventionrepresent an improvement over the carbonate-sulfonate product in that ithas improved high temperature stability properties. These products showan improvement even over the formated derivaties in the water stabilitytest. The products of this invention may find utility in the lubricationof automobile engines and in the diesel engines, such as used in trucks,ships and railroads. These derivatives may be used in both mineral oilsand synthetic oils, such as esters and polyolefin fluids and the like.The lubricant formulations containing the derivatives of this inventionmay also be used in greases in which conventional thickeners areemployed. Other additives may also be employed along with thesederivatives as indicated in the water stability test, includingantioxidants, pour point depressants, and the like. Oil compositionscontaining a minor amount, from 0.05% to about 50% by weight of theadditive, find suitable use in the lubricating field. The compounds ofthis invention may be also used in aqueous emulsions, such as used inmetal working operations.

Although the preparation and utility of certain of the products and oilcompositions containing them have been set forth in detail, the presentinvention is not in any way limited to these specific embodiments butsuitable modifications can be made therefrom without departing from thescope of the invention.

Having described our invention, we claim:

1. An oil-soluble overbased metal sulfonate liquid product obtained bythe process comprising reacting an alkaline earth metal carbonateoverbased alkaline earth metal sulfonate product, which possesses ametal content of at least 200% higher than that of the correspondingnormal metal sulfonate salt, with formic acid and a C to C carboxylicacid at a temperature of from 50 to 225 C., wherein the mole ratio offormic to the said C to C carboxylic acid is in the range of from about40:1 to about 1:4, wherein the total acid equivalents are sufficient tosubstantially completely convert the metal carbonate component to thecorresponding metal formate- C to C carboxylate, and wherein the formicacid is reacted with the metal carboxylate prior to reaction with the Cto C carboxylic acid.

2. The product of claim 1 wherein the mole ratio is from 10:1 to 1:3.

3. The product of claim 1 wherein the C to C carboxylic acid is aceticacid.

4. The product of claim 1 wherein the C boxylic acid is aceticanhydride.

5. The product of claim 1 wherein the formic acid is reacted portionwiseand the C to C carboxylic acid is reacted after the first portion offormic acid.

6. The product of claim 1 wherein the alkaline earth metal is calcium.

7. The product of claim 1 wherein the reactions are carried out in thepresence of a diluent.

8. The product of claim 7 wherein the diluent is a lubricating oil. I

9. A lubricating oil composition containing a minor amount sufiicient toimpart detergency thereto of the product of claim 1.

10. The method of preparing the product of claim 1 comprising (1)reacting an oil-soluble alkaline earth metal carbonate-overbasedalkaline earth metal sulfonate product, which possesses a metal contentof at least 200% higher than that of the corresponding normal metalsulfonate salt, with formic acid in a proportion less than thatsufficient to convert the metal carbonate component to metal formate,and (2) reacting the reaction mixture of step (1) with a C to Ccarboxylic acid to substantially convert the remaining metal carbonatecomponent to the metal C to C carboxylate, said reaction steps beingcarried out at a temperature of from 50 to 225 C., the mole ratio offormic acid to C to C carboxylic acid being from about 40:1 to about1:4.

11. The method of claim 10 wherein step (1) and step (2) areinsufficient to completely convert the metal carbonate component to themetal formate-C to C carboxylate, and step (2) is followed by step (3)reacting the remaining metal carbonate component from the reactionmixture of step (2) with formic acid.

12. The method of claim 11 wherein the amount of acids in steps (1), (2)and (3) is insufficient to completely convert the metal carbonatecomponent and step 3) is followed by step (4) reacting the remainingmetal carbonate component with a C to C acid.

13. The method of claim 10 wherein the C to C acid is acetic acid.

14. The method of claim 10 wherein the C to C acid is acetic anhydride.

15. The method of claim 10 wherein the alkaline earth metal is calcium.

16. A fuel composition comprising a normally liquid hydrocarbon fuel anda minor amount sufiicient to impart detergency thereto of the product ofclaim 1.

to C car- References Cited UNITED STATES PATENTS 3,242,079 3/1966McMillen 252-33 PATRICK P. GARVIN, Primary Examiner.

US. Cl. X.R. 44-70

